When did NEC last allow use of natural gas fired emergency power system

[Natfuelbilll]

When did the NEC last allow using a natural gas emergency power system ?

Or conversely, when did the NEC first require language in 700.12(B)(2) requiring not less than 2 hours of onsite fuel supply?

 

[ptrip]

I'm embarrassed to admit that I didn't even know that was there.

I see that verbiage back to 1999 NEC.

Quote from 2008 NEC:
700.12 (B) (2):
Internal Combustion as Prime Movers. Where internal combustion engines are used as the prime mover, an on-site fuel suppy shall be provided with an on-premise fuel supply sufficient for not less than 2 hours' full-demand operation of the system.

700.12 (B) (3):
Dual Supplies. Prime movers shall not be solely dependent on a public utility gas system for their fuel supply or municipal water supply for their cooling systems. Means shall be provided for automatically transferring from one fuel supply to another where dual fuel supplies are used.
Exception: Where acceptable to the AHJ, the use of other htan on-site fuels shall be permitted where there is a low probability of a simultaneous failure of both the off-site fuel delivery ssytem and power from the outside electrical utility company.

---

These same paragraphs are repeated in 701: Legally Required Standby Systems

What is a Prime Mover? I don't see it listed as a definition in 100 or at the beginning of 700.

Does this actually mean that a natural gas generator cannot be used as an emergency (or legally required standby) generator?

I'm having a hard time believing it.

edit: Just glanced at the 2008 Handbook ... there are no clarifications to these paragraphs.

 

[ptrip]

Further reading in the handbook yielded:

Supply systems fo remergency systems can be designed as one or more of the following:
(1) Storage batteries ....
(2) A generator set driven by a prime mover, acceptable to the AHJ, and with adequate capacity to carry the max load connected. Prime movers may be internal-combustion engines...
Off site fuel supplies such as natural gas or piped steam may be used where experience has demonstrated their reliability. Off-site fuel supplies may also be used where they will provide greater reliability than gasoline or diesel engines or in isolated areas where maintenance or refueling could be a problem.
...
:-?
Now ... the handbook comments are not enforceable ... but it seems contradictory ... and in line with the reasoning why I've it's common around here to see natural gas emergency generators.

 

[iwire]

We still use NG quite often for true emergency systems without any on site fuel supply. I suggest talking to your AHJ.

 

[MNWildcat]

AHJ approval

AHJ approval

With local AHJ approval, it is realtively normal to have a NG gen for LS loads. Though it may be harder to propose that for a hospital occupancy. Plus size (cost) makes it unlikely.

 

[dereckbc]

We still use NG quite often for true emergency systems without any on site fuel supply. I suggest talking to your AHJ.

Ditto, AL NG gensets I have installed use the utility supply.

 

[steve66]

When did the NEC last allow using a natural gas emergency power system ?

Or conversely, when did the NEC first require language in 700.12(B)(2) requiring not less than 2 hours of onsite fuel supply?

Keep reading until you get to the exception that Ptrip listed. I think it depends a lot on geographical area and your AHJ. Around here, earthquakes aren't too much of a concern, and natural gas generators are ocassionally found.

 

[zbang]

What is a Prime Mover? I don't see it listed as a definition in 100 or at the beginning of 700.

The component of a power plant that transforms energy from the thermal or the pressure form to the mechanical form.
or
A machine or mechanism that converts natural energy into work.

The term is often used where there are multiple things that transform energy, such as a railway locomotive, where there are both a combustion engine and electric motors driven by the output of that engine.

 

[hillbilly1]

I have seen them both ways, in fact the 30 kw I have on my house is a dual fuel, It runs on natural gas normally, and automatically switches over to propane if the primary source.(I only have propane, so I run it on the backup source) I think it's the fire marshall making the requirement, I've seen them 20 miles apart, and one require it, the other doesn't.

 

[iwire]

I have seen them both ways, in fact the 30 kw I have on my house is a dual fuel, It runs on natural gas normally, and automatically switches over to propane if the primary source.(I only have propane, so I run it on the backup source) I think it's the fire marshall making the requirement, I've seen them 20 miles apart, and one require it, the other doesn't.

hillbilly, the genset at your house is not an emergency generator to the NEC so there is no rule about on site fuel. :smile:

 

[weressl]

hillbilly, the genset at your house is not an emergency generator to the NEC so there is no rule about on site fuel. :smile:

Newsflash!

Hillbilly OVERULES NEC in his own home and wins!


:grin:

BTW piped gas and local propane tank for dual fuel engine is a prefect setup.